Process of crosslinking polymers



United States Patent 3,404,134 PROCESS OF CROSSLINKING POLYMERS RichardWatkin Rees, Wilmington, Del., assignor to E. I. du Pont de Nemours andCompany, Wilmington, Del., a corporation of Delaware No Drawing.Continuation-impart of applications Ser. No. 168,839, Jan. 25, 1962, andSer. No. 271,477, Apr. 8, 1963. This application Feb. 28, 1964, Ser. No.348,293 The portion of the term of the patent subsequent to Aug. 2,1983, has been disclaimed 7 Claims. (Cl. 26078.5)

ABSTRACT OF THE DISCLOSURE The process of ionically cross-linkingcopolymers containing carboxylic acid groups by adding thecation-supplying material at elevated pressure and at a temperature ofabove the melting point of the copolymer.

This application is a continuation-in-part of application Ser. No.168,839, filed Jan. 25, 1962, now abandoned and application Ser.271,477, filed Apr. 8, 1963, now U.S. Patent No. 3,264,272. U.S. PatentNo. 3,264,272 is a continuation-in-part of application Ser. No. 135,147filed Aug. 31, 1961, now abandoned.

This invention relates to the process of producing ion linkedcopolymers.

Ion linked hydrocarbon polymers are described in Belgian Patent 621,846,and U.S. patent application Serial No. 168,839. Ion linked hydrocarboncopolymers as described in the Belgian patent are copolymers of alphaolefins and alpha, beta ethylenically unsaturated carboxylic acids inwhich some carboxylic acid groups have been neutralized with metalliccations. The ion linked copolymers described in U.S. patent applicationSerial No. 168,839 are copolymers of alpha olefins and alpha, betaethylenically unsaturated carboxylic acids in which some of thecarboxylic acid groups havve been neutralized with amine cations. Theterm neutralized as used in the Belgian Patent and the U.S. applicationis defined as that reaction that takes place between the metallic oramine cations and the carboxylic acid groups of the copolymer. Acomparison of the infrared spectrum of the unreacted copolymer with thatof the reacted (neutralized) copolymer explains to some extent thenature of this neutralization reaction. Such a comparison shows theappearance of an absorption band at about 6.4 microns which ischaracteristic of the ionized carboxyl group, COO-, a decrease in thecrystallinity band at 13.7 microns and a substantial decrease, dependingon the degree of neutralization, of a band at 10.6 microns,characteristic of the unionized carboxyl group, COOH. It thereforeappears that the properties of these reacted copolymers is the result ofan ionic attraction between the metal ion or the amine and one or moreionized carboxyl groups.

It is one of the objects of this invention to provide a process for theproduction of the ionic copolymers disclosed in this Belgian patent andin the U.S. patent application.

The process of the present invention comprises mixing a copolymercontaining polymerized alpha olefin units and polymerized alpha, betaethylenically unsaturated carboxylic acid units with a metallic or aminecation supplying material under such conditions that some of thecarboxylic acid groups are neutralized.

The process of this invention may be carried out in many different typesof apparatus and using many different reaction media. Specificially, theprocess of this invention may be carried out by dissolving the copolymerto be neutralized in a suitable solvent, and then introducing the cationthat reacts with the carboxylic acid group into the solution. Theprocess of the present invention may also be carried out by meltblending the copolymer to be neutralized with a material that will yieldmetallic or amine cations. The melt blending operation may take placeusing a rubber mill or an extractor extruder. The process of the presentinvention may also be carried out using a slurry process in whichparticles of the copolymer to be neutralized are slurried in a liquidcontaining the ion which reacts with the carboxylic acid groups. Also,the process of the present invention may be carried out by injection ofcations into the polymerization reactor in which the copolymer has beenformed, while the polymer is still molten or in solution.

In any of the specific processes of ionically linking the copolymer, itis necessary that some of the metallic or amine cation supplyingmaterial be dissolved in the reaction media under the reactionconditions.

The copolymers which may be crosslinked by the process of the presentinvention comprise at least one alpha olefin unit having the generalformula where R is a radical selected from the class consisting ofhydrogen and hydrocarbyl radicals having one to eight carbon atoms andat least one alpha, beta ethylenically unsaturated carboxylic acid unithaving one to two carboxylic acid groups. Preferably, the alpha, betaethylenically unsaturated carboxylic acid unit has 3 to 8 carbon atoms.The concentration of the alpha olefin unit in the copolymer is at least50 mol percent and preferably greater than mol percent. Theconcentration of the alpha, beta.- ethylenically unsaturated carboxylicacid unit in the copolymer is 0.2 mol percent to 25 mol percent,preferably from 1 to 10 percent. Specific alpha olefin units useful inthe copolymers include: ethylene, propylene, butene-l, styrene,pentene-l, hexene-l, heptene-l, 3 methylbutene-l, and 4 methylbutene-l.Specific alpha, beta ethylenically unsaturated carboxylic acid unitsuseful in the copolymers include: acrylic, methacrylic, ethacrylic,itaconic, maleic, fumaric, monoesters of dicarboxylic acid such as ethylhydrogen fumarate, and maleic anhydride. Maleic anhydride and otheralpha, beta ethylenically unsaturated anhydrides are considered acidsfor the purposes of the present invention.

The preferred process for preparing the copolymers for use in theprocess of the present invention is direct copolymerization. This may beachieved by introducing the monomers into a polymerization environmentmaintained at high pressures, 50 to 3000 atmospheres, and at elevatedtemperatures, to 300 0., together with a free radical polymerizationcatalyst. An inert solvent such as water or benzene may be employed inthe polymerization environment. Random distribution of carboxylic acidgroups in all the polymer molecules is best obtained by directcopolymerization. Particular processes for the production of thecopolymers are known in the art and described in the literature.

The copolymers may also be obtained by grafting an alpha, betaethylenically unsaturated carboxylic acid to a polyolefin base, or byconversion of a copolymer of a polyolefin and a derivative of carboxylicacid to the free acid.

The copolymers which are ion linked by the process of the presentinvention are preferably of high molecular weight. Molecular weight issuitably defined by melt index, a measure of viscosity described indetail in ASTM-D-l238-57T. The melt index of the copolymers preferred inthe present invention is within the range of 0.1 to 1000 g./10 min.

The acid copolymer need not be a two component 3 polymer. Thus, althoughthe olefin content of the copolymer should be at least 50 mol percent,more than one olefin can be employed to provide the hydrocarbon natureof the copolymer, also more than one alpha, beta ethylenicallyunsaturated carboxylic acid may be employed. Additionally, any thirdcopolymerizable monomer can'be employed in combination with the olefinand the carboxylic acid comonomer. Preferred termonomers are vinylesters and acrylates, i.e., alkyl acrylates and methacrylates having upto eight carbon atoms, such as vinyl acetate, vinyl propionate, methylmethacrylate and ethyl acrylate. The scope of base copolymers suitablefor use in the present invention is illustrated by the followingexamples:

Ethylene/ acrylic acid copolymers, ethylene/methacrylic acid copolymers,ethylene/itaconic acid copolymers, ethylene/methyl hydrogen maleatecopolymers, ethylene/ maleic acid copolymers, ethylene/ acrylicacid/methyl methacrylate copolymers, ethylene/methacrylic acid/ methylmethacrylate copolymers, ethylene/itaconic acid/ methyl methacrylatecopolymers, ethylene/methyl hydrogen maleate/ethyl acrylate copolymers,ethylene/methacrylic acid/vinyl acetate copolymers, ethylene/acrylicacid/ vinyl alcohol copolymers, ethylene/propylene/acrylic acidcopolymers, ethylene/ styrene/ acrylic acid copolymers,ethylene/methacrylic acid/acrylonitrile copolymers, ethylene/fumaricacid/vinyl methyl ether copolymers, ethylene/vinyl chloride/acrylic acidcopolymers, ethylene/vinylidene chloride/acrylic acid copolymers,ethylene/vinyl fluoride/methacrylic acid copolymers,ethylene/chlorotrifiuoroethylene/methacrylic acid copolymers,ethylene/methacrylic acid/ acrylic acid copolymers, andethylene/methacrylic acid/maleic anhydride copolymers.

The copolymers may also, after polymerization but prior to ioniccrosslinking, be further modified by various reactions to result inpolymer modifications which do not interfere with neutralization.Halogenation of a copolymer is an example. Blends of the alpha olefin,alpha, beta ethylenically unsaturated carboxylic acid copolymer withother alpha olefin, alpha, beta ethylenically unsaturated copolymers, orwith other hydrocarbon polymers may be crosslinked by the process ofthis invention.

The cations useful in reacting with the carboxylic acid groups may besupplied as water soluble salts, or as insoluble compounds that can beconverted to soluble salts by the addition of another reactant. Thecations should have an effective valence of one to three. The termeffective valence as used herein means that the cation forming materialis readily ionized to form cations having a valence in the range of oneto three, but that the cation forming material is not readily ionized toform cations having more than three valence charges; in other words, thecation is complexed to such an extent that the number of ionic chargesis in every case in the range of 1 to 3. The preferred complexed metalions are those in which all but one of the metal valences are complexedand one is readily ionized. Such compounds are in particular the mixedsalts of very weak acids, such as oleic and stearic acid, with ionizableacids, such as formic and acetic acid.

The uncomplexed metal ions which are suitable for use in the process ofthe present invention comprise mono-, diand trivalent ions of metals inGroups I, II, III, IV-A and VIII of the Periodic Table of Elements (seepage 392, Handbook of Chemistry and Physics, Chemical Rubber PublishingCo, 37th ed.). Uncomplexed monovalent metal ions of the metals in thestated groups are also suitable in forming the ionic copolymers of thepresent invention with copolymers of olefins and ethylenicallyunsaturated, dicarboxylic acids. Suitable monovalent metal ions are NeK+, Li+, Cs+, Ag Hg+ and Cu+. Suitable divalent metal ions are Be, Mg+ cn +2 +2 +2 +2 +2 +2 p +2 w Co Ni+ and Zn. Suitable trivalent metal ionsare Al+ Sc+ Fe+ and Y.

The complexed metal ions which are suitable for use in the process ofthe present invention are di, tri, tetra and hexavalent ions that havebeen complexed so that their effective valence is withinthevrange-of 1to .3, preferably 1. Suitable metal ions are the divalent andtrivalent-dons listedabove, tetravalent ions suchas :Tir Zr, Hf-+ V+ Ta,W+ and hexavalent ions such as Cr+- Ce, and Pe Suitablecomplexing'agents include' ste'arate, oleate, salicylate, and phenolateradicals.

The amine cations which are suitable for use in the process of thepresent invention have the general formula:

wherein R is selected from the class consisting of hydrogen and alkylradicals having 1 to 5 carbon atoms, R" and R are selected from thegroup consisting of hydrogen, alkyl radicals having 1 to 5 carbon atomsand alkylene radicals having 2 to 10 carbon atoms when R" and R arecombined, 11 is an integer from 1 to 10, m is an integer from 0 to 4,and X is selected from the group consisting of a carbon-carbon bondwhere X does not exceed 30 carbon atoms, a divalent oxygen radical, adivalent sulfur radical, an imine radical, a-carbonyl radical and aphenylene radical.

The metallic cations can be added to the copolymer in the form of salts,oxides, hydroxide carbonate, free metal, metal hydride, metal alkoxideor organometallic compounds. If the metallic cation producing materialis readily soluble in water at the reaction conditions, a considerabledegree of reaction between metallic ions and the carboxyl groups willtake place. The equilibrium of the reaction can be shifted to favor thisreaction by removal of the anionic portion of the cation producingmaterial as soon as it has become associated with the acid hydrogen. Ifthe cation producing material is the salt of a very weak acid such assodium resorcinol, the equilibrium of the reaction is sufficiently infavor of the formation of ion links, and no steps need to be taken toremove the anionic portion of the cation producing material from thecopolymer.

If the metallic cation producing material is only slightly soluble atthe reaction condition, it is necessary to remove the anionic portion ofthe cation producing material. This removal is readily accomplished byvolatilizing or otherwise removing the anionic portion as soon as it hasbecome associated with the acid hydrogen. It is therefore necessary thatthe slightly soluble metal cation producing material be selected so thatthe anionic portion may be readily removed.

If the metallic cation producing material is substantially insolubleunder the reaction conditions, it is desirable to' convert the insolublematerial into a soluble or slightly soluble one in situ to acceleratethe reaction. This may be readily accomplished in the case of metaloxides, hydroxides and carbonates by the addition of acidsuch 'as aceticacid, lactic acid, propionic acid, and mixturesof these acids.

The amine cation may be added to the copolymer in perazine, diethylenetriamine, beta,'beta diaminodiethylj ether, ta, beta-diaminodiethylthioether, and phenylene diethyl amine. I

The diamines may also be added to theicopolyiners, of

the present invention in the form of their ammonium salts which have thegeneral formula wherein R, R", R, X, m and n have the same meaning asabove and where A- is an acid radical. The reaction of the ammoniumsalts with the acid copolymers employed as reagents in the presentinvention differs slightly. In the reaction of the diamine with thecarboxylic acid group to form the ammonium salt and thereby the diaminemodified copolymer, no by-products of any kind are formed. However, inthe reaction of the described ammonium salt with the carboxylic acidgroup of the copolymer to result in the diamine modified copolymer, aside product H+A- is formed. Since this reaction is an equilibriumreaction, it is necessary, in order to drive the reaction to completionand to obtain the ammonium salt formation with the acid groups of thecopolymer, that the product H+A- be of such a nature that it can bereadily and completely removed from the reaction environment. It is, ingeneral, therefore, preferred to employ ammonium salts in which the acidradical forms a product with the hydrogen of the carboxylic acid groupof the copolymer which can be readily volatilized from the reactionmixture at reaction conditions. In particular, diammonium formates,acetates, methoxides, ethoxides, carbonates, and bicarbonates arepreferred. The product of these acidic radicals with hydrogen can bereadily volatilized from a mixture of the ammonium salt and the basecopolymer. The reaction product of the acid copolymer and a diamine isidentical to the reaction product obtained from the reaction of the basecopolymer with an ammonium salt in which the acid radical is volatilizedduring the reaction with a base copolymer. Hence, both reaction productsare considered diamine ion linked carboxylic acid copolymers.

The preferred metals, regardless of the nature of the acid copolymer arethe alkali metals. These metals are preferred because they result in ionlinked copolymers having the best combination of improvement in solidstate properties with retention of melt fabricability. It is notessential that only one metal ion be employed in the formation of theionic copolymers; in fact, more than one metal ion may be preferred incertain applications.

The quantity of ions employed or the degree of neutralization willdiffer with the degree of solid property change and the degree of meltproperty change desired. In general, it was found that the concentrationof the cation should be at least such that the cation neutralizes atleast percent of the carboxylic acid groups in order to obtain asignificant change in properties. As explained above, the degree ofneutralization for optimum properties will vary with the acidconcentration and the molecular weight of the copolymer. However, it isgenerally desirable to neutralize at least 50 percent of the acidgroups. The degree of neutralization may be measured by severaltechniques. Thus, infrared analysis may be employed and the degree ofneutralization calculated from the changes resulting in the absorptionbands. Another method comprises the titration of a solution of the ioniccopolymer with a strong base. Excess quantities of the cation do not addto the properties of the ionic copolymer of the present invention, sinceonce all carboxylic acid groups have been ionically crosslinked, nofurther crosslinks are formed.

As stated earlier, the ionic crosslinking reaction may take place in aslurry. In carrying out this reaction in a slurry, it is desirable thatthe copolymer will stay submerged. Copolymer to be crosslinked is mixedwith a liquid containing the cations to be used to crosslink. Theconcentration of the ions in the liquid is preferably 2 to 4 times thatstoichiometrically necessary to neutralize a predetermined amountgreater than 10% of the acid groups of said copolymer. The slurry shouldbe maintained at a temperature within the range of 50 to 100 C. Highertemperatures within this range favor more rapid neutralization, but alsofavor more liquid absorption by the copolymer. The liquid used for theslurry may be any solvent for the cation forming material, but suitablesolvents are water, lower aliphatic alcohols, such as methyl ethyl,propyl and butyl, and mixtures of these lower aliphatic alcohols witheach other and/ or water. The time of reaction will, of course, dependupon the temperature, the concentration of the cations, the pellet sizeof the copolymer and the desired degree of neutralization; however, thetime will generally be between one-half hour and 8 hours. The pelletsize of the copolymer may vary from less than 100 mesh pellets togreater than li -inch cubes. The pellets are not uniformly neutralized,for the carboxylic acid groups in the polymer molecules on the surfaceof the pellet will be totally neutralized, while those in the polymermolecules located at the center of the pellets will be substantiallyunneutralized.

Some of the liquid is absorbed by the pellets, and this must be removed.This may be conveniently accomplished by means of an extractor extruder,in which the liquid is volatilized.

In the following examples which illustrate the slurry process, all partsand percentages are in parts by weight unless otherwise stated.

EXAMPLE 1 300 grams of an ethylene methacrylic acid copolymer containing90 weight percent ethylene and 10 weight percent methacrylic acid havinga melt index of 5.8 g./ 10 min., an ultimate tensile strength of 3400p.s.i., and a percent elongation of 550 in the form of 60 mesh pelletsWere introduced into 1500 g. of a 3.6 Weight percent sodium hydroxideaqueous solution, under the following conditions with the followingresults:

Time (min.) Temp. C.) Tensile Elong. M.I.

(p.s.l.) (percent) EXAMPLE 2 300 g. of a 90% ethylene 10% methacrylicacid copolymer as in Example I in the form of mesh pellets were slurriedin 1500 g. of methanol containing 3.6 weight percent sodium hydroxide,under the following conditions 55 with the following results:

Time (min) Temp. C.) Tensile Elong. M.I.

(p.s.i.) (percent) EXAMPLE 3 carried out using a solution process, inwhich process the copolymer is dissolved in a solvent and reacted withcations contained in the solvent. Suitable solvents for the copolymerare aromatic hydrocarbon solvents such as xylene, benzene and toluene,or chlorinated hydrocarbon hexamethylene diamine and the resultingreaction mixture was agitated for 15 minutes at the temperatureindicated. The product was recovered by precipitation with methanol andwashed thoroughly with water and acetone. The dried diamine copolymerwas compression molded and was a solvents such as carbon tetrachloride,tetrachloroethylene found to have a significantly higher transparencythan the d tfichlofoethylene or h d b l t h a unmodified copolymertested under the same conditions. cyclohexane, hexane, ethylene, etc.,and mi t r f The resiliency of the modified copolymer was greatlyinthese. Viscosity modifiers such as lower aliphatic alcocreased y thereaction of the diamine With the p hols, surfactants and the like may beincluded. This reac- 10 tion is best carried out at temperatures of 80to 120 C. EXAMPLE 11 The cation producing material is usually added inthe form an aqueous Solutioh- To a solution of 50 of hi h densit ol ethlene con- The cations react with the acid groups substantlally raining4.3% of acrylii acid grafted the ieb y b; peroxide stolchiometrrcallyand substantially lnstantaneously; thus, 15 fti having a melt index f 51 min in 2 g the degree of crosslinking can be predetermined by selecofxylerie was added at a temperature f C. tion of the amouht of Canonadded; of hexamethylene diamine. The reaction was continued at Thecohcehtl'atloh of the Polymer m the soluhoh may that temperature for 20minutes with agitation. The revary Widely- It is usually Preferred tohave about 10% sulting diamine modified copolymer was found to have byweight polymer in the solvent, but this is not critical. substantiallythe same melt index but on molding resulted The copolymhr 15 h? femovedfrom shhltloh; thls in a molding of increased stiffness and highertensile propy be done by preclpltahohi evaporation and the erties. Thetransparency of the moldin was measurably copolymer dried to removesolvent, water, etc. The dryincreasedv a ing operation may beaccomplished in a drying oven, but is preferably carried out in anextractor extruder. 25 EXAMPLES 12 TO 15 In the following examples whichillustrate the solution process, all parts and percentages are in partsby weight Using the reaction procedure set forth in Examples 4 unlessotherwise stated. to 9, an ethylene/methacrylic acid copolymer contain-0 ing 118 wgight fpercent/og methacrylic acid and having I) a met in ex0 .3 g. 1 mins. was treated with 5 10, EXAMPLES 4 To 9 and 18% by weightof hexamethylene diamine. Mdlded samples of the resulting isolateddiamine modified co- Solutions of g. batches of an ethylene/methacrylicpolymer were found to be transparent and resilient. The acid copolymercontaining 10 weight percent of methmodified copolymers were subjectedto tensile and stiffness acrylic acid and having a melt index of 5.8g./1O min. 3t) tests. The results shown in Table II were obtained.

TABLE II Wt. percent Melt index in Stifiness Yield strength UltimateUltimate Example hexamethylene g./l0 min. in p.s.i. in p.s.i. strengthelongation diamine in p.s.i. in p.s.i.

2 ASTM-D-412-57T.

EXAMPLES 16 TO 23 Employing the procedure of Examples 4 to 9 with themethacrylic acid copolymer therein used, the diamines listed in thetable below were reacted with the acid copolymer to result in diaminemodified copolymers. The resulting products were compression molded into60 mil sheets and compared to the unmodified copolymer in their meltindex, stiffness and tensile properties. The resulting data are comparedin Table III. As can be seen from these TABLE I Percent hexamethyleneYield Ultimate Elonga- Resilience Example diamine Melt index Stifinessstrength tensile tion 1 in Transparency (bend rein g.ll0 min. in p.s.i.in p.s.i. strength 1 percent (visu eovery) Weight Stoichiometric 1np.s.1.

0 0 5. 8 9, 900 890 3, 414 550 Hazy Limp. 1 15 3. 9 18, 950 1, 3, 525440 Slight haze Fair. 2 30 4. 9 20, 340 l, 3, 740 443 Very slighthaze... D0. 5 74 4. 8 24, 220 1, 320 3, 880 450 00d. 10 148 5. 2 38, 4001, 600 3, 423 370 Very good. 15 223 5. 2 40, 000 1, 734 3, 560 380 D0.

1 ASTMD-74758T. 2 ASTM-D-412-51T.

7 0 data, paraphenylene diamine having a dissociation con- EXAMPLE 10 Toa solution of 50 g. of an ethylene/acrylic acid copolymer containing 5weight percent of acrylic acid and having a melt index of 10 g./l0 min.in 250 ml. of xylene stant of 1 10 results in a diamine modifiedcopolymer which shows borderline improvement over the unmodifiedpolymer. This borderline improvement is further apparent from thetransparency of the modified copolymer as well maintained at atemperature of 130 C. was added 3 g. of 7 as its infrared spectrum andits resiliency.

TABLE III Diamine Melt index in Stifiness in Yield strength Exampleg./10 min. p.s.i. in p.s.i.

Type Wt. percent Dlss. Const.

16 5. 8 9, 900 890 17 Dietliylene trlamine. 4 3. 5 22, 700 1,315 18Ethylene diamine 3. 5 5. 8 13, 300 1,150 19... Piperazine 20 6.4Xl 5.418, 000 1, 170 20 p-Phenylene diamlne 25 1. 1X10- 5. 3 16,100 1, 160 21.N,N'-diisopropy1 hexamethylene diamine. 12 5. 3 29,000 1,800 22-Decamethylene diamine 12 4. 9 31,440 1, 730 23 N,N-tetramethylhexamethylene diarmne 15 5. 5 28, 000 1, 400

EXAMPLE 24 An ethylene-methacrylic acid copolymer containing 18 weightpercent of methacrylic' acid and having a melt index of 6.3 g./ min. wasmodified with 18 weight percent of diethylene triamine using thesolution procedure described in the foregoing examples. The resultingdiamine modified copolymer was found to have a stiffness of 43,650p.s.i. compared to a stiffness of 16,400 p.s.i. for the unmodifiedcopolymer and an ultimate strength of 5,200 p.s.i. compared to anultimate strength of 5,000 p.s.i. for the unmodified polymer.

Example 24 was repeated except that instead of the diethylene triamine,ethylene diamine was employed. The resulting diamine modified copolymerwas found to have a stifiness of 41,650 p.s.i., as compared to astilfness of 16,400 p.s.i. for the unmodified copolymer.

EXAMPLE 25 Employing the procedure of Examples 4 to 9, 50 g. of anethylene/methacrylic acid copolymer containing 10% by weight ofmethacrylic acid and having a melt index of 5.8 g. was reacted with 5 g.of bis(p-aminocyclohexyl) methane. The product was isolated by methanolprecipitation. The resulting dried product was compression molded andstiffness and tensile properties were measured. The melt index of themodified copolymer was 4.4 g./1O min. The stiffness of the modifiedcopolymer was measured to be 40,400 p.s.i. as compared to 9,900 p.s.i.for the unmodified copolymer. The yield strength was measured to be1,880 p.s.i. as compared to 890 p.s.i. for the unmodified copolymer. Thetransparency of the modified copolymer was greatly improved over that ofthe unmodified copolymer on the basis of mold ed samples.

1 ASTM-D-747-58T.

EXAMPLE 26 To a solution of 50 g. of an ethylene/methacrylic acidcopolymer containing 10 weight percent methacrylic acid and having amelt index of 5.8 g./l0 min. in 250 ml. of xylene maintained at atemperature of 100 C. was added 3 grams of strontium hydroxide dissolvedin 50 ml. of water. Gelation followed immediately. The product wasrecovered by precipitation with methanol and washed thoroughly withwater and acetone. The product was dried in a drying oven. The producthas a melt index of 0.19 g./ 10 min. Glass clear moldings were made fromthe copolymer.

As stated earlier the process of the present invention can be carriedout in an extractor extruder. When carneutralization reaction is withinthe range of 100 to 290 C. and the pressure on the constituents is inthe range of 100 to 10,000 p.s.i. The material that forms cations may beadded to the copolymer as an aqueous solution, or in a substantially dryform. The process as carried out in the extractor extruder is acontinuous one, that is, copolymers and cation-forming material are fedcontinuously into the extruder and ion linked copolymer is continuouslyremoved from the extruder. At pressures of 100 to 5000 p.s.i. and attemperatures of 100 to 290 C. the mixing action of the extruder produceswhat appears to be a single phase mixture, thus assuring a uniformdegree of neutralization.

The process in the extractor extruder can be divided roughly into foursteps which steps correspond to the zones in the reactor. In the firstzone the copolymer is thoroughly mixed at high pressure and heated toabove its melting point, cation-forming material may be present in thiszone. In the second zone neutralization of the carboxylic acid groupstakes place. If the cationforming material was not present in the firstzone, it is added at this point. The copolymer then passes to a thirdzone, a zone of reduced pressure in which the volatile materials in thecopolymers, for example, water and acid formed when the copolymer wasneutralized with an acid salt, are vaporized and removed. The copolymerthen passes to a fourth zone in which the polymer is removed "from theextractor extruder. There may be more than one zone of a particular typeand the zones may be of different dimensions.

EXAMPLES 27-3 4 To the feed opening of a 2-inch plasticating extruderWere fed as separate streams, pellets of a copolymer of ethylene andmethacrylic acid and a metal compound substantially insoluble in themolten polymer. The feed rate of the resin varied from 15 to 22 lbs/hr.The screw was made up of an S-diameter long plasticating section, a 13.5diameter long mixing section of the type described in US. Patent3,006,029, a throttle ring to allow pressure to be maintained in themixing section, a S-diameter long extraction section and a 4-diameterlong pumping section. At the inlet of the mixing section an acidsolution was injected into the molten resin. The melt temperature atthis point was 156 C. and the pressure was 400 p.s.i. The mixture wasallowed to react in the mixing section, after which the molten mixtureat a tempreature of 210 C., passed over the throttle ring into theextraction zone. The melt was devolatilized under a vacuum of 27 in Hg.

ried out in an extractor extruder the temperature of the Subsequently,the dried, molten ion linked resin was ex- TABLE IV Acid copolymer Metalcompound Acid solution Product Example Weight Melt Feed Volume FeedProduction Melt percent of index, Stiffness, Type rate, Type percentrate, rate, index, Stiflness, methacrylic g./10 min. p.s.i. 1b./hr.aqueous ccJmin. lb./hr. g./10 min. p.s.i.

acid solution 15 71 12, 250 ZnO. 0. Propionic acid 50 5. 29 16. 5 1. 5244, 650

15 71 12, 250 Z110"... 1. 05 Acetic acid 100 6. 0 18. 5 0. 28 52, 480

15 71 12, 250 Zn0 1. 49 Methacrylic acid 60 9. 17 17. 5 0. 19 63, 760

15 71 12, 250 ZnO 1. 18 Lactic acid 60 5. 15. 8 0. 29 60, 340

15. 3 6. 3 24, 250 ZnO- 1. 12 Acetic Acid- 50 5. 22 22 0. 13 63, 040

Isopropanol- 25 15. 3 6. 3 24, 250 ZnO. 1.07 Heptanoic ac 61. 9 9. 0 220. 16 45, 060

Acetic acid"-.. 22. 7

10 Zn0 0.89 --do-...-.- 50 4. 83 19.1 2. 64

=9 178 Zn0 0.36 do 50 5.5 13.5 25

ilerpolymer of: 67% ethylene, 24% vinyl acetate and 10% methacrylic acilerpolymer of: 70% ethylene, 20% vinyl acetate and 9% methacrylic acLactic acid does not completely solubillze ZnO under the conditions ofthe reaction. Further mixing will result in complete solubilization.

To the feed opening of a 3.5 inch plasticating extruder were fed, asseparate streams pellets of ethylene methacrylic acid copolymer and adry powdery mixture, de-

diameters in length, in series. The first extraction zone was maintainedat '27 in. "of'Hg afid thseiidiid'at 28 in. Hg. The temperature of themelt was maintained between 270 C. and 280 C. The extraction zoneremoved the volatile constituents from thelmolten, ion linked copolymer.The polymer was pumped out through a diein the form of strands, whichwere cooled inwat er and cut into pellets. r Y

The specific operating details, the reagents employed and some of thepolymer properties affected are'shown in fined as premix composition, ofone or more metal com- Table V.

TABLE V Mcthacrylie acid copolymer Premix composition Example Metalcompound Weight per- Melt index, Stitlness, p.s.i. copolymer,Stabilizer, Feed rate, cent acid g./10 min. parts parts lb.lhr.

Type Parts g z 39 11.7 5.9 18,400 7. 5 E 8 :1 0.20 3.16

I i z 9. 5 4. 3 14, 000 s. 04 7 23 0. 01 1. 66

15. 3 6. 3 24, 250 8. 74 4. 54 0. 14 2. I 15. 3 0. a 24, 250 s. 64 4. 410. 01 1. 74

Acid Product Example 7 Aqueous solution oi Volume percent Feed rate,cc./min. Rate, lb./hr. Melt index, gJlO Stiffness, p.s.i.

min.

35..- Acetic acid 40 13.8 55 0.7 36, 600 36 .do 40 13. O 47 0.52 38, 380

38 do s 37 13. 5 54 1. 72 34, 420

Lactic ac 3. 8 39 Acetic acid 40 13. 0 57 0.37 37,000

pounds, finely divided copolymer and equal parts of dilaurylthiodipropionate and dodecylpentaerythritol diphosphate as stabilizer.In the extruder, the plastic pellets were melted and conveyed along withthe crudely incorporated premix to the mixing section. The initialplasticating screw was 7 diameters long and maintained at a temperatureof about 158 C. At the inlet of the mixing section an acid solution wasinjected into the molten stock by means of a nozzle penetrating thebarrel wall. The mixing section was of the type described in US. PatentNo. 3,006,029 and was 13 diameters long. In the mixing sectionmaintained at a temperature of 270 to 280 C., the premix compositionreacted with the polymer melt to neutralize the acid groups of thepolymer through the formation of a soluble metal salt.

At the end of the mixing section the mixture of ion linked copolymer andreaction by-products passed through a pressure-control valve and atransfer line into a 2-inch diameter extraction extruder. The stocktemperature before the valve was 280 C. and the pressure 750 p.s.i. Thisextruder had two extraction zones, each about 4 EXAMPLES 4346 Theethylene/methacrylic acid copolymer employed in the foregoing exampleswas extruded through a two inch extruder equipped with mixing torpedoesand an injection device in the extruder barrel. The resin was extrudedat 30 rpm. (screw speed) and a melt temperature of to 180 C.Hexamethylene diamine in the concentration indicated was injected intothe mixing section of the extruder. The stifiness and tensile propertiesof the resulting products obtained at the three levels of hexamethylenediamine concentration were determined on 60 mil sheets made from theextruded product. The data obtained are shown in Table VI and comparedwith the unmodified copolymer. It was observed that in the experiment inwhich 10 weight percent of hexamethylene diamine was added the mixingaction of the extruder employed was insufficient to assure completedistribution and reaction of the hexamethylene diamine added. Theaddition of the hexamethylene diamine in all three concentrations didnot significantly affect the extrusion behavior of the copolymer.

TABLE VI Weight percent Melt index Stiffness Yield strength r UltimateElongation Example methylene in g./10 min. in p.s.l. in p.s.i. strengthvin percent 1.

diamine in p.s.i.

13 EXAMPLE 47 High molecular weight, commercially availablepolypropylene was oxidized with molecular oxygen to result in theformation of peroxygen groups in the polymer. The

14 ness over products produced under the same condition but without theaddition of hexamethylene diamine.

As stated earlier, the process of this invention can be carried out on amill. The copolymer is milled at a temture above its melting pointpreferably 110 to 160 resultlng product was then reacted w1th acrylicacid unt1l para a graft copolymer of polypropylene containing 3% of C.,and then cat1o n form1ng material is added to the coacrylic acid wasobtained. The graft copolymer had a Polymer the minmg confirmedPreferably i melt 'index of 13 g no minutes The resulting product 1onforming material is added as an aqueous solution, for was extruded in a2 inch extruder equipped with mixing s gi w i i the i g i torpedoes andan injection device at a screw speed of 30 1c Wa er vaponzes. wa er preen Glen y rpm and a temperature of 190 to 6 Approxi long that theneutralizatlon reaction takes place. The 3% of hexa methylene diaminewas injected into neutralrzatlon react1on is substantiallystolchiometrlc so the melt in the mixing section of the extruder. Theresultthe e canon to be addfzd can be Predeter-mmed' ing extrudate wasgreatly improved in transparency and The 1011 crosslinked copolymer 1sthen removed from the resilience. Compression molded samples of thematerial 15 were significantly stilfer as compared to the unmodified Infonqwmg Whch Illustrate the process copolymer. No significant change inthe extrusion beof mventlon us.mg a an indfimemages havior of thecopolymer was found as a result of the are m Parts by Welght unlessotherwlse mdlcated' add1t1on of hexamethylene d1am1ne. EXAMPLE 60EXAMPLES 48 57 A 500 g. sample of an ethylene/methacrylic acid co-Ethylene methacrylic acid copolymers were ionically polymer, containing10 weight percent of methacr-ylic acid linked using aqueous solutions ofsodium hydroxide, in and having a melt index of 5.8 g./10 min. (ASTM-D-an extractor extruder under the conditions shown in the 1238-57T) wasbanded on a 6 inch rubber mill at 150 Table VII with the results asshown in Table VII. C. After the copolymer had attained the milltemperature,

TABLE VII Base resin P d t Solution Product properties R tConditionsinreaetion zone eae 01' Example Percent MI, Stifiness, at fCone, Flow MI, Stiffness, extruder, Melt, 'Iemp., Pressure, Screw MMAg./1O min. p.s.l. lbs/hr. percent rate, g./10 mm. p.s.l. diam., in. in0., out p.s.l. speed,

ccJmin. r.p.m.

As previousl stated, the rocess of this invention may 24 g. of sodiummethoxide dissolved in 100 ml. of methay a I P I I I u I be carried outb injection of cation forming matenal n01 was added to the copolymerover a period of 5 mmc I I u I 0 into a olymerization reactor,immedlately after the poutes as workmg of the copolymer on the m1ll wasconp I I n o I l I I n lymerizati-on reaction is completed. Thepolymerizatlon tinned. Melt blending of the composltlon was continuedreaction is usually carried out at temperatures within the for anadditional 15 minutes during which time the initialrange of 150 to 300C. and at pressures within the range ly soft, fluid melt became stiffand rubbery on the m1ll. of to 3Q00 atmospheres using a free radicalpolymeri- However, the polymer could still be readily handled on zationcatalyst. The cations will react stoichiornetrically the mill. Theresulting product was found to have a melt under these conditions. Thepressure is then released, index of less than 0.1 g./ 10 minutes andresulted in transflashing 01f most of the volatile components; theremain- 50 parent, as compared to opaque for the copolymer base, der ofthe volatile components may be removed from the moldings of greatlyimproved tensile properties. polymer. This may be accomplished by adrying oven EXAMPLE 61 and/ or an extractor extruder.

, To 50 g. of an ethylene/methacrylic ac1d copolymer EXAMPLE 5 55containingt 1 0 gveightt gegcen/tlcaf methacrylic1 1aclid and havmg a mein ex 0 g. mi-nu es mi e at a tem- 251521521552 6 2.1 5 rttssaz aaa r a;on a mm a e gra ua y g. 0 magnesium acetate (X 4H O) g f benzoyld g i" a,i in 25 ml. of water. Milling was continued for 15 minutes p fy 'z' f gg i ggg g gfg P is filgggzg 2 53' at which time the evolution of aceticacid had ceased. The

roduct h d It .12 After the reaction was complete, but before thepressure Eulted in s s f g 'i g g no mmutes and re was let olf, a 20 g.solution of sodium hydroxide in 100 ml. of water was introduced into thereactor and the pres- EXAMPLE 62 sure let down 10 seconds later. Theproduct was dried T o 50 g. of an ethylene/itacomc ac1d copolymerhavfsi.3.2525216125415555215;121:6551125:; a of 9 a 3 of 1 g 10 minWithout the addition of sodium hydroxpercent by Welght of the cop-olymerof ace-n and was ide the melt index would have been about 3 3 10gradually-added 3 of sodlum hydroxlde m 20 of mirmtes water while thepolymer was being worked on a 6-inch rubber mill at a temperature of 150C. Upon addition of EXAMPLE 59 the hydroxide, the polymer melt becamestiff, transparent The process of the previous example was repeated, andelastomenc' EXAMPLE 63 I .3 only this time 20 g. hexamethylene diaminewere added to the copolymer prior to letting ofi the pressure. The To 50g. of a copolymer of ethylene and maleic anproduct had improvedtransparency, toughness, and stiffhydride, containing 7 weight percentof copolymerized maleic anhydride and having a melt index of 8.5 g./ 10minutes, being milled on a rubber mill ata temperature of 135 C., isadded 22.8 g. of zinc monoacetate monostearate. After 15 minutes on themill a transparent, tough, resilient polymer product is obtained havingsufficient melt flow for fabrication into film by standard meltextrusion. Repeating the experimental procedure with zinc acetate anintractible resin is formed within'10 min utes of milling, preventing.further milling. The resin could not be extruded into a film usingstandard melt extrusion.

EXAMPLE 64 To 50 g. of a copolymer of ethylene and methacrylic acid,containing 10 weight percent of copolymerized methacrylic acid andhaving a melt index of 5.8 g./l minutes, being milled on a rubber millat 130 C. are added the following components in the order indicated: (a)3.25 g. zinc oxide, (b) 11.7 g. stearic acid, and (c) 2.5 g. of aceticacid. Only after the addition of the acetic acid does the melt becomeclear and an increase in viscosity is observed. After minutes of furthermilling the copolymer is removed. Although the melt index is reduced,the resulting ionic copolymer is suitable for melt fabrication.

EXAMPLE 65 An ethylene/methacrylic acid copolymer containing 10 percentmethacrylic acid was handed on a tWo roll mill at 170 C. and 3.6 weightpercent of powdered sodium hydroxide was added over a period of 2minutes. Milling was continued over a period of 10 minutes to ensurehomogeneity. The ionic copolymer obtained was reduced more than tenfoldin melt index and was glass clear and resilient. When extruded as amelt, the ionic copolymer could be drawn into fibers having pronouncedelastic recovery.

EXAMPLE 66 A 500 g. sample of an ethylene methacrylic acid copolymercontaining 10 weight percent methacrylic acid and having a melt index of5.8 g./ 10 minutes was milled on a 6-inch rubber mill at 150 C. Afterthe copolymer had attained the mill temperature, 30 g. of hexamethylenediamine were added to the copolymer over a 10 minute period as themilling was continued. The blending was continued for 10 more minutes.The melt index of the product was not substantially changed. But thepolymer was transparent. The stiffness measured to from about 10,000p.s.i. to about 29,000 p.s.i. and the yield strength from about 900p.s.i. to about 1600 p.s.i.

The high molecular weight ion linked copolymers prepared by thedescribed process can be extruded into films of excellent clarity,fibers of outstanding elasticity and resilience, pipes with superiorstress-crack resistance, wire coatings with improved cut-throughresistance and good dielectric properties despite the presence of metalions, and foamed sheets; they can be further injection molded intointricate shapes and closely retain the dimension of the mold; they canbe vacuum formed, blow molded and compression molded with greater easeand better properties than linear hydrocarbon polymers. Ion linkedcopolymers can, furthermore, be drawn and uniaxially or biaxiallyoriented. Ionic copolymer surfaces are printable and adhere well toadhesives commercially available. Thus, they can be laminated to paper,metal foil and other plastic surfaces. The adhesion of the ioniccopolymer is so good that they themselves can be employed as adhesives.Low molecular weight ionic copolymers, particularly, are useful for suchpurposes. Many other uses and modifications of the ion linked copolymersof the present invention will be apparent from the foregoing descriptionand it is not intended to exclude such from the scope of this invention.

I claim: 4

1. A process of ionically cross-linking copolymers formed bycopolymerizing at least one alpha-olefin of the general formula RCH CHwhere R is a radical of the class consisting of hydrogen and hydrocarbylradicals having one to eight carbon atoms, and at least one alpha,beta-ethylenically unsaturated carboxylic acid having one to tWocarboxylic acid groups and three to eight carbon atoms, the alpha-olefincontent of said copolymers comprising at least 50 mol percent of saidcopolymer, the alpha,betaethylenically unsaturated acid content of saidcopolymer comprising 0.2 to 25 mol percent of said copolymer, whichcomprises mixing said copolymer with a cation supplying material at apressure of 100 to 10,000 p.s.i. and a temperature above the meltingpoint of the copolymer and between 100 C. and 290 C., so that the cationsupplying material forms cations, the cations having an effectivevalence of one to three, the number of cations formed being sufficientto neutralize at least 10 percent of the carboxylic acid groups, andneutralizing at least 10 percent of the carboxylic acid groups in thecopolymer.

2. The process of claim 1 in which the process is a continuous processin which the polymer is continuously advanced from one step to another.

3. A process for the preparation of ion-linked copolymer whichcomprising copolymerizing at least one alpha.- olefin having the formulaRCH CH at least one alpha, betaethylenically unsaturated carboxylic acidhaving one to two carboxylic acid groups and having three to eightcarbon atoms, at a temperature between and 300 C. and at a pressurewithin the range of 50 to 3000 atmospheres with a free-radicalpolymerization initiator to form a copolymer having an alpha-olefincontent of greater than 50 mol percent, and an alpha,-beta-ethylenicallyunsaturated carboxylic acid content of between 0.2 mol percent and 25mol percent, adding a cation supplying material to the polymer prior toreleasing said pressure, under such conditions that the cation formingmaterial is ionized to form cations selected from the class consistingof metallic cations having an effective valence of l to 3 and amineions, releasing said pressure and removing volatile constituents fromthe copolymer.

4. A process of ionically cross-linking copolymers formed bycopolymerizing at least one alpha-olefin having the formula RCH=CH whereR is a radical of the class consisting of hydrogen and hydrocarbylradicals having one to eight carbon atoms, and at least one alpha,beta-ethylenically unsaturated carboxylic acid, having one to twocarboxylic acid groups, and three to eight carbon atoms, thealpha-olefin content of the copolymer comprising at least 50 mol percentof the copolymer, the alpha,beta-ethylenically unsaturated carboxylicacid content of said copolymer comprising 0.2 to 25 mol percent of saidcopolymer to a predetermined degree by neutralizing a predeterminedamount greater than 10% of the acid groups with cations, which comprisesmixing said copolymer with a cation supplying material under suchconditions that the cation supplying material is ionized to form cationsof the class consisting of metallic cations, having an effective valenceof 1 to 3 and amine cations, at a temperature above the melting point ofthe copolymer and between C. and 290 C. and at a pressure of 100 to10,000 p.s.i., the quantity of cations being sufiicient to neutralize atleast 10 percent of the resulting mixture, removing volatileconstituents from the mixture by reducing the pressure, and recoveringionlinked copolymer.

5. The process of claim 4 which is operated continuously.

6. The process extractor extruder.

7. A process of ionically crosslinking a polymer formed bycopolymerizing at least one alpha-olefin of the general formula RCH CHwhere R is a, radical of the class of claim 5 which is carried out in anconsisting of hydrogen and hydrocarbyl radicals having one to eightcarbon atoms, and at least one alpha,betaethylenica-lly unsaturatedcarboxylic acid having one to two carboxylic acid groups and three toeight carbon atoms, the alpha-olefin content of said polymer comprisirigat least 50 mol percent of said polymer, the alpha, beta-ethylenicallyunsaturated acid content of said polymer comprising 0.2 to 25 molpercent of said polymer which comprises milling said polymer and addingthe metallic cation -forming material in solution at a temperature abovethe melting point of the polymer and at atmospheric pressure. p

References Cited UNITED STATES PATENTS Graham 260-86] Rees 26078.5 Bowen260-785 Tanner 204-15916 Brown 260--78.5 Bowen 260-785 10 JOSEPH L.SCHOFER, Primary Examiner.

I. KIGHT, Assistant Examiner.

